1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of Prior Art
As a means for solving environmental problems, it is required for electronics equipments and apparatus in offices to decrease energy consumption. In order to decrease energy consumption, for example, auto-shut-off function is provided for turning off the power supply of an apparatus or of a part thereof when the apparatus is not operated for a predetermined time.
In a prior art copying machine having auto-shut-off function for turning off the power supply of the entire apparatus, the power supply is turned off irrespectively of the situation. For example, a trouble such as paper empty or paper jam which inhibits to continue image forming may happen while the user is not present before the copying machine. Even in such a situation, the power supply of the entire apparatus is turned off after a predetermined time passes. In a conventional copying machine, image forming conditions such as paper size, copy number, image density and the like are set before a copy job is started. Therefore, when the power supply of the entire apparatus is turned off, the user who returned before the copying machine has to turn on the power supply and, for example, supply papers in a paper cassette to solve the trouble. Then, the user has to set image forming conditions again before the copy job is restarted. This is inconvenient for the user.
In order to solve this problem, a copying machine may have resume function besides the auto-shut-off function. In the resume function, data on image forming are stored in a backup memory when the power supply is turned off. When the power supply is turned on again, the situation when the power supply is turned off is realized again based on the data stored in the memory. Then, the user can continue image forming soon in the same image forming conditions as those before the power supply is turned off. Then, copying operation can be performed efficiently.
However, the user who operates the copying machine after the power supply has been turned off by the auto-shut-off function is not necessarily the same person. Let us assume, for example, that a trouble such as paper empty happens while the user is not present before the copying machine. If the same user turns on the power supply again, the resume function is effective because the user can restart image forming readily after solving the problem. On the other hand, if a different user turns on the power supply again, the resume function sets image forming conditions which have been set by the previous user. Then, the image forming conditions may be different from the conditions used by the different user. In this case, the different user first resets the image forming conditions and sets new image forming conditions suitable for him or her. Thus, the resume function is inconvenient in this case. Further, in an apparatus where image data as well as image forming conditions are also saved when the power supply is turned off, a different user who turned on the power supply again can output the image dealt by the previous user. This is a problem for secret documents.